1. Summary of the Invention
This invention relates to an improved orthopedic weight monitor, and more particularly, to an orthopedic weight monitor having a flexible pad shaped to conform to the inside of a shoe or to be incorporated into a cast or splint with a sensor encased within the heel portion of the pad and a electronic module positioned remotely from the sensor for receiving signals from the sensor by way of an electrical coupling between the sensor and the electronic module.
2. Description of the Background Art
In the field of orthopedic weight monitors, there have been a variety of devices designed to facilitate the detection and/or monitoring of weight bearing on a lower extremity, whether a foot, leg, hip or the like, for medical purposes. A patient who has any kind of medical condition that necessitates restriction of the weight bearing capacity of their lower extremities is doctor instructed not to apply any more than a specific amount of weight to the affected lower extremity until the condition of the extremity has changed. The goal is to help educate the patient, to inform the attending doctor, and to monitor the patient's adherence to the amount of weight applied to the lower extremity. This monitoring device is most beneficial and would have excellent therapeutic benefits.
Commonly, when patients with a lower extremity disability are undergoing rehabilitation training, the amount of weight bearing on the lower extremity in the early stages of treatment is limited. There is an optimum course of progress of weight bearing to yield the most effective and expedient healing of patient suffering from a lower extremity condition. By way of example, patients with fractures, grafts, joint replacements or soft tissue injury should be encouraged to apply moderate pressures to the affected area for encouraging rapid healing. Whereas, excessive pressures on the affected area will adversely effect healing.
Therefore, there exists a variety of reasons why it is medically desirable to determine if any, or at what levels, weight is being born by the affected bone. Historically, patients have been instructed to press down on a scale device to a prescribed load for optimum healing of the patient's injury. Further, the patient is instructed that while walking he should visualize the scale and the amount of effort required to achieve the prescribed scale loading and to apply that same loading while walking to promote proper healing of the affected bone. Unfortunately, the scale method is not an effective method for the patient to judge the proper amount of pressure that should be applied to the affected extremity. There is no form of feedback which is essential to aid the attending physician. Also the scale method only provides static loading input to the patient. The static loading is extremely difficult for the patient to equate to the dynamic loading of the extremity under walking conditions. Furthermore, it can be extremely difficult to reproduce the desired loading on a consistent basis. Finally, many patients have sensation depravation or less than adequate sensations in the lower extremities to adequately equate the results from the scale method to walking conditions.
The present invention is directed to provide for improved devices which detect and monitor weight bearing by feet, legs or hips done in a manner which is safe, secure, clean, economical and aesthetically pleasing.
Throughout the United States steps are being taken to improve upon devices for the detection and monitoring of weight bearing by feet, legs or hips for medical orthopedic purposes. The prior art discloses several types of orthopedic weight monitors. By way of example, U.S. Pat. Nos. 3,702,999 to Gradisar, 4,745,930 to Confer and 4,647,918 to Goforth disclose weight monitoring devises.
Two force sensitive electrical conductors disposed, one each, in predetermined locations beneath the heel and ball of the foot of a user are illustrated in '999. The conductors comprise a pair of flat circular metal plates which are separated by a resilient member. The contacts within the conductor are spaced apart form each other and are of a generally flat circular shape. An elastomeric ring is disposed essentially between the contacts. Therefore, the plates are held apart from each other by the resilient member. Furthermore, the upper plate has a threaded nut secured thereto for engaging a set screw. As force is applied to the conductors, the elastomeric compresses causing the set screw to engage the lower plate to complete an electrical circuit. A flat braided flexible wire extends along the top side of the sole pad and is connected to the top contact within each of the conductors in the toe and heel. A second flat braided flexible wire extends along the bottom side of the sole pad and is connected to the bottom contact within each of the conductors in the heel and toe. The device relies on adjustment of the set screw to vary the amount of force required to complete the electrical circuit. The disclosure teaches a pair of electrical contacts spaced apart from one another by an elastomeric material. The contacts cannot provide a thin profile that is required to facilitate a thin pad or insole to be placed under a patient's foot for optimal performance of the orthopedic weight monitor. The thickness of the mechanical conductors creates a bulky orthopedic monitor which impedes the patient's normal walking gate. Additionally, because of the mechanical nature of the conductor, variations in performance are inherent in the conductor due to material wearing and aging. Furthermore, the flat braided flexible wire is not able to provide the user of the monitor with an easily concealable device.
An orthopedic weight monitor relying on a multi-layered assembly is taught in '930. An insole having three overlaying sheets of a plastic material bonded together is disclosed. The intermediate sheet has cut-outs of the heel, toe and ball portions of the sole to create three separate internal chambers. A plurality of fingers formed of conductive ink forms a mechanical switch. The conductive ink is disposed on the outer layers of plastic and contact each other as force is applied to the assembly to signal pressure is being applied to the patient's foot. As a result of the close proximity of the layers of plastic material, the performance of the switches is subject to variations resulting from wear of the plastic layering material and the shoe that is used as a carrier for the assembly. Additionally, as a patient heels there are no provisions for varying the amount of pressure required to cause a signal. An entire new monitor must be adapted to the patient to vary the amount of pressure required to produce a signal.
Furthermore, '918 discloses a plurality of transducers for measuring the pressure at a number of points as a function of time. Each of the transducers is connected to a microprocessor. The device is particularly adapted to the problem of diabetics who experience low blood pressure levels over a period of time. The device uses a number of transducers located throughout a foot pad. The device is a multi-event notification system for informing a user when any number of sensing points reaches a preselected threshold of pressure over a time interval. There is no provision for, or teaching of, a device to warn the user of an excessive instantaneous application of pressure. The devise is designed to monitor a large number of pressure points. Therefore, the device is not suitable for economical application because of the complexity of the device.
In an article in Medical & Biological Engineering & Computing, Sept. 1978, an article titled "Limb-Load Alarm Device for Partial-Weight-Bearing Walking Exercise" a device was disclosed for measuring the limb load with two removable load transducers attached to the sole of a patients shoe. The transducers are constructed of a rectangular plate supported by a plurality of neoprene rubber sponges. Each sponge has a vinyl chloride sheet adhered to a lower wear surface of the sponge. The transducer relies on the plate flexing between the supporting sponges to determine the amount of loading the user is subjecting a limb. The article does not teach, nor suggest, the applicant's invention that uses a flexible pad material to continuously supported a plate for determining the amount of lower extremity loading. Furthermore, the transducer described in the article is 7 millimeters thick and thereby curtails use in a shoe sole. The thickness of the transducers interferes with the normal gate of a patient that is fitted with the transducer. There is no teaching of the transducer used in the Applicant's invention which is easily inserted into the shoe of the user and does not interfere with a patient's normal gait.
A flexible force sensor having an electrical conductor releasably attached to a test site is disclosed in U.S. Pat. No. 4,426,884 to Polchaninoff. The sensor has a plurality of relatively spaced hemispherical electrical contacts and conductors supported such that when a force is applied to the sensor, electrical resistance is produced as a function of the applied force. The disclosure relies on an induced change in electrical resistance to measure forces. The sensor comprises an electrode platform and flexible conductive sensor. The disclosure teaches a platform and sensor that are releasable attached to a test site for the determination of forced applied to the test site. Because the sensor is releasably attached to test site, there is no teaching of an orthopedic monitor that is easily positioned by a layman or impaired patient. Furthermore, the flexible and dynamic nature of the patient's foot during walking inhibits proper attachment of a sensor directly to the patient's foot. Additionally, the mechanical nature of the sensor makes the disclosure susceptible to failures resulting from excessive pressure and repeated flexing.
Other methods of warning a patient when a predetermined load has been reached in a lower extremity are illustrated in U.S. Pat. Nos. 3,791,375 to Pfeiffer and U.S. Pat. No. 3,974,491 to Sipe. Fluid containing load cells are disclosed in '375. The load cells are located below the ball and heel of a patient's foot. As pressure is applied to the cells, fluid is forced from the chamber as a function of the load applied by the patient's foot. The disclosure teaches a bellows connected to the cells via tubes to measure the flow out of and into the cell for determining the amount of load a lower extremity is subjected. Additionally, a single resilient liquid filled tube within a resilient foot pad adapted to fit inside a shoe is disclosed in '491. The monitoring device is controlled by pressure resulting from compression on the flexible tubing. Both disclosures '375 and '491 are susceptible to failure from punctures to the fluid bladders. Furthermore, the mechanical nature of fluid transfer within a tube and the size of the tubing required to transfer load information to a monitoring device precludes easy concealment or remote location of the tubing and sensing devices.
Finally, U.S. Pat. No. 3,658,052 to Alter discloses a device for the detection of movement by attaching a magnet to an object to be monitored. The disclosure teaches a pickup coil located such that movement by the object having the magnet attached to it induces a voltage in the coil. The output from the coil is delivered to a circuit where pulses are generated for signalling an alarm. The disclosure makes no provision for portability since the motion of an object can only be detected by a stationary coil. Furthermore, there are no provisions for determining any information other than movement relative to the coil. There is no teaching to monitor the amount of pressure applied to a lower extremity for orthopedic purposes.
As illustrated by the background art, efforts are continuously being made in an attempt to improve orthopedic weight monitors. No prior effort, however, provides the benefits attendant with the present invention. Additionally, the prior patents and commercial techniques do not suggest the present inventive combination of component elements arranged and configured as disclosed and claimed herein.
The present invention achieves its intended purposes, objects, and advantages through a new, useful and unobvious combination of method steps and component elements, with the use of a minimum number of functioning parts, at a reasonable cost to manufacture, and by employing only readily available materials.
Therefore, it is an object of this invention to provide an improved orthopedic weight monitor for detecting weight bearing on a lower extremity for medical purposes, comprising in combination: a flexible pad having a thickness of between about 1/8 and 1/4 inches shaped for conforming to the bottom of a human foot for placement inside of a shoe or incorporated into a cast or splint, the pad having a heel portion and a toe portion, the heel portion located cooperable with the heel of a user; a sensor encased within the heel portion of the pad to be located beneath the heel of the user, the sensor comprising a thin, rigid rectangular plate and a foil strain gage coupled therebeneath, the plate having two opposing exterior edges which are turned inwardly to form support peripheral edges; an electronic module remotely positioned from the sensor and removably coupled to the body of the user for receiving signals from the foil sensor, wherein the electronic module signals the user to a prescribed level of weight bearing by at least one of the following methods: vibration, sound, light, continual analog and digital; and electrical lines extending to exterior of the pad between the sensor and the receiver, the electrical lines being removably coupled to both the sensor and electronic module.
Another object of the invention is to detect the amount of weight bearing on a patients foot to monitor the effect upon a lower extremity prosthesis, fractures of the lower extremity, bone grafting, soft tissue pathology during the healing process of the patient which is healing and/or other conditions in a safe, secure, convenient and economical manner.
A further object of this invention is to provide a rapid, reliable method of notifying a patient when a prescribed weight load limit on the worked limb has been reached for proper rehabilitation.
A further object of this invention is to readily indicate to a patient unadvised weight bearing despite the loss of most other senses by the patient.
A further object of this invention is to adjust the initiate point of a signal to the patient depending on the individual weight bearing situation of the particular patient at that time.
A further object of this invention is to allow for a physician and/or patient to calibrate and recalibrate a weight detecting monitor to retain accuracy.
A further object of this invention is to record, alert and/or educate a patient to levels of weight bearing by vibration, sound, light, continual analog readout or digital readout.
A further object of this invention is a variant ability to produce a record of the patient's activities to indicate the time and duration of pressures which comply or exceed that recommended by the physician.
A further object of this invention is to add or delete from a weight monitor in order to adjust the sophistication of the alerting and recording functions to address the changing physical needs and/or economic strictures of an individual patient.
A further object of this invention is to monitor a patient who requires life term monitoring of weight bearing.
A further object of this invention is to weight monitor a patient's normal environment providing a notification signal presented as sound, light or vibration, whichever is most suitable to the patient's environment.
A further object of this invention is to generate in a rehabilitation center environment a signal that can be monitored remotely by a therapist for aiding in patient progress analysis.
A further object of this invention is to provide, where medically indicated, a monitor that can be modified to provide two signals, a first for acceptable loading and a second for overloading.
A further object of this invention is to monitor and record for medical and/or insurance reasons, a monitor to record each load bearing to indicate over-use/over-loading or inactivity and under-loading.
The foregoing has outlined some of the more pertinent objects of this invention. These objects should be construed to be merely illustrative of some of the more prominent features and applications of the present invention. Many other beneficial results can be attained by applying the disclosed invention in a different manner or by modifying the invention within the scope of the disclosure. Accordingly, other objects and a fuller understanding of the invention may be had by referring to the summary of the invention and the detailed description of the preferred embodiment in addition to the scope of the invention defined by the claims taken in conjunction with the accompanying drawings.